The present invention relates generally to hand power tools.
The German document DE 195 47 332 A1 discloses a hand power tool, in which a cylindrical housing is composed of two synthetic plastic housing shells with edges forming separation edges which together define a horizontal separation plane. The housing shells are connected with one another by screws. In the interior of the housing, an electric motor with an impeller is arranged, whose drive shaft is supported at its ends by ball bearings in the housing shells and fixedly connected with a bevel pinion for joint rotation. The pinion engages with a bevel plate wheel supported on a driven shaft and having a rotary axis extending perpendicular to the drive shaft.
The driven shaft has a bearing point which is remote from the tool and has a ring shaped sliding bearings inserted in a cylindrical bearing receptacle of a housing shell. Furthermore, the driven shaft has a bearing point which is close to the tool and has a sleeve-shaped bearing bushing with a needle bearing. An eccentric pin supported on the end of the driven shaft which is close to the tool extends through the bearing bushing from above into an opening of a connecting rod-type driver. The driver engages with a projection in a recess of an insert tool which is supported through a guiding bearing in a front region of the housing shells.
Accordingly, it is an object of present invention to provide a hand power tool which is a further improvement of the existing tools of this type.
The inventive hand power tool has a motor arranged in a housing and having a drive shaft which is supported with its ends via a corresponding bearing in at least one component, and is connected via a driver element with an insert tool by an operative connection.
In accordance with the present invention it is proposed that at least one bearing of the drive shaft is supported over a part of its length in a radial direction via a sliding seat directly on the component and through a part of its length in a radial direction via a synthetic plastic ring on the component, with preferably over ⅓ of its length via the sliding seat and over approximately ⅔ of its length via the synthetic plastic ring or a rubber ring. The drive shaft is reliably fixed by the sliding seat and in addition can be advantageously dampened via the rubber ring in its bearing point or vibrations or impacts can be compensated by the rubber ring. Furthermore, an outer ring of the bearing can compensate, through the synthetic plastic ring or rubber ring, the tolerances of the sliding seat, and fixed radially and non rotatably by clamping.
The synthetic plastic ring in accordance with the present invention is form-lockingly connected with the component at least opposite to its mounting connection, and in advantageous manner over the whole periphery. The synthetic plastic ring can be connected with the component in a particularly simple, cost-favorable manner without additional components, because of the form-locking connection. In particular in the hand power tools which are subjected to jerk-like movements, as for example during a so-called scraping and the like, it can be reliably avoided that the synthetic plastic ring is displaced in an axial direction from the component and thereby negatively affects the support.
The bearing is fixed in an axial direction preferably via a housing part, whereby additional components, mounting space, mounting expenses and cost can be saved. Holding elements can be formed simply and cost favorably on a screw dome of the housing which frequently extends in an interior of the housing. With the design provided with holding ribs, a cooling air stream can flow through the hand-power tool. By the form-locking connection of the synthetic plastic ring, it can be advantageously reliably fixed without extending the holding ribs over the whole periphery and negatively affecting the cooling stream.
The form-locking connection between the synthetic plastic ring and the component can be formed by different formations which are generally known for a person skilled in the art, for example by steps, zigs, waves, etc. In a simple and cost favorable manner, the form-locking connection can extend at least in one radial direction in a collar engaging in a recess, wherein the collar can be arranged on the synthetic plastic ring and/or on the component.
In accordance with a further embodiment of the invention, it is proposed that the synthetic plastic ring at least has an outer contour with a diameter increasing in mounting direction, and the housing part has a corresponding inner cone. Due to the cone, a desired form-locking connection can be provided in an axial direction and in addition, because of an axial force on the synthetic plastic ring, a radial force onto the bearing is applied, and thereby it is fixed especially secure by the synthetic plastic ring.
In order to avoid that the synthetic plastic ring can be mounted turnably, it is preferably formed symmetrically in an axial direction to its central plane, and the component has a corresponding symmetrical opposite surface. This can be achieved with a centrally arranged collar, or advantageously with a symmetrical double cone.
When the double cone in an axial direction has a diameter increasing to its central plane, the synthetic plastic ring during the mounting in an axial direction is automatically compressed in a radial direction so that the mounting can be simplified. The double cone on the synthetic plastic ring can be however formed with a diameter which also reduces in an axial direction to the central plane.
For preventing turning of the synthetic plastic ring in the component, it can be connected form-lockingly in a peripheral direction with the component. The connection can be formed for example by projections extending in the axial direction.
The component can be formed by an additional component which receives the bearing force, and is directly or indirectly supported in the housing. Preferably however, the component can be formed by a housing part, whereby additional components and mounting expenses can be saved. The bearing of the drive shaft is advantageously arranged in a cup-shaped recess. Various thermal expansions can be avoided by a different materials, and a tilting of the drive shaft can be avoided in this manner.
The inventive solution can be utilized in different hand power tools, for example a power drill, an angle grinder, etc., and especially advantageously with hand power tools which are subjected to jerk-like movements, such as scrapers, impact drill, impact screwdriver, etc.
The novel features which are considered as characteristic for the present invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.